IN THE ESNA-IDFU REGION, NILE VALLEY, EGYPT 249 



appearance of G. velascoensis velascoensis (Cushman) is used to mark the base of the 

 Upper Paleocene, while its complete disappearance marks the dawn of the Eocene. 



Globorotalia whitei Weiss 

 (PL 23, figs. 3«-c) 



1928 Globigerina crassaformis Galloway & Wissler ; White : 193, pi. 27, figs, iqa-c. 



1935 Globorotalia crassaformis (Galloway & Wissler) Nuttall : 130, pi. 15, figs. 21, 29. 



1955a Globorotalia whitei Weiss : 18, pi. 6, figs. 1-3. 



1 955b Globorotalia whitei Weiss ; Weiss : 308, pi. 1, figs. 29, 30. 



19576 Globorotalia wilcoxensis Cushman & Ponton ; Bolli : 79, pi. 19, figs. 7-9. 



x 959 Globorotalia whitei Weiss ; Hamilton & Rex : 794, pi. 253, figs. 1,2. 



Description. Test medium-sized, planoconvex, strongly umbilico-convex, 

 coiled in a very low trochospire ; dorsal side very weakly inflated or almost flat ; 

 ventral side strongly inflated and distinctly protruding ; equatorial periphery roughly 

 ovoid, distinctly lobate ; axial periphery bluntly angular ; chambers on the dorsal 

 side about 9 in number, arranged in 2 dextrally coiled whorls ; the initial chambers 

 are small, globular, compressed, and almost masked by the surface rugosity ; the last 

 whorl is composed of 4, large, roughly ovoid chambers which increase rapidly in size, 

 and are elongated in the direction of coiling ; on the ventral side the chambers are 4, 

 large, subglobular in the early part and roughly ovoid later, strongly inflated and 

 increase rapidly in size ; sutures on the dorsal side, short, slightly curved and depres- 

 sed ; on the ventral side they are long, straight, radial and strongly incised ; umbilicus 

 small, deep and open with the ventral sutures radiating from it in an X-shaped 

 pattern ; aperture interiomarginal, extraumbilical-umbilical ; wall calcareous, 

 perforate ; surface distinctly papillose or even nodose, with the nodes sometimes 

 tapering out to form stout, spine-like projections, especially along the periphery. 



Dimensions of described specimen. 



Maximum diameter = 0-38 mm. 

 Minimum diameter = 0-30 mm. 



Thickness = 0-26 mm. 



Remarks. Globorotalia whitei was described by White (1928) and Nuttall (1935) 

 as Globigerina crassaformis Galloway & Wissler and as Globorotalia crassaformis 

 (Galloway & Wissler) respectively. However, G. crassaformis is a Pleistocene form 

 which is completely different from the present species. 



Bolli (19576) described as G. whitei Weiss, from the lower Lizard Springs formation 

 of Trinidad, forms which are different from the original description and figures of 

 Weiss. On the other hand, he described as G. wilcoxensis Cushman & Ponton a form 

 which most probably belongs to G. whitei. 



Globorotalia whitei is distinguished by its medium-sized, umbilico-convex test ; 

 its small number of chambers per test and in the last whorl, subangular axial 

 periphery, narrow umbilicus, X-shaped ventral sutures and very rough surface. 

 It is believed to have evolved from Globorotalia esnaensis (Le Roy) by the flattening 

 of the dorsal side, the development of the subangular axial periphery, and the 

 change of the surface spines into stout knobs. It is also believed to have evolved into 



